Use the Formula for the General Term of a Geometric SequenceUse the formula for the general term (the nth term)of a geometric sequence to find the indicated term of the
sequence with the given first term, $$\mathbf { a } _ { 1 }$$ , and common ratio, r.
-$$8,24,72,216,648 , \ldots$$
A) $a _ { n } = 8 ( 3 ) ^ { n - 1 }$
B) $a _ { n } = 8 ( 3 ) ^ { n }$
C) $a _ { n } = a _ { 1 } + 3 ^ { n }$
D) $a _ { n } = 8 ( 3 n )$

Question

Quizplus · Accepted Answer

The common ratio is 3 since each term is obtained by multiplying the previous term by 3. The first term is 8. Using the formula for the general term of a geometric sequence: 
$$a_n = a_1 \cdot r^{n-1}$$ 
we have: 
$$a_n = 8 \cdot 3^{n-1}$$
Therefore, the correct choice is A, which matches this formula.

Use the Formula for the General Term of a Geometric a1\mathbf { a } _ { 1 }a1​

Use the Formula for the General Term of a Geometric $\mathbf { a } _ { 1 }$